Dengue and dengue hemorrhagic fever result from the infection with any of the four serotypes of dengue viruses. Dengue is endemic in Puerto Rico and has become a global and public health problem. Research is needed to develop an effective and vaccine that will prevent infection and disease caused by any of these viruses. Thus, the objective of thee studies is to develop an effective dengue-D DNA vaccine. Our long-term objective is to develop a tetravalent dengue DNA-based vaccine. Our vaccine strategy is focused on the dengue envelope because this protein mediates the early binding and entry steps in infection. Neutralizing antibodies (Nab) against this protein were shown to be protective against pathogenic virus infection and disease. Dengue envelope expression vectors will be constructed and tested for immunogenicity in Balb/c mice. These DNA vectors will be evaluated alone or in combination with genetic adjuvants for their respective abilities to induce immune responses (Nab and CTL) that will protect vaccinated mice against intracranial dengue-2 virus infection. Standard molecular biology techniques (such as PCR and cloning) will be used to construct the individual DNA expression cassettes. Immune responses will be monitored by ELISA, virus neutralization assays and CTL assays. Efficacy studies (i.e. challenge) will also be performed. Results obtained from these studies will give important information for the design and development of DNA vaccines expressing the envelope protein of dengue-1, dengue-3 and dengue-4.